Epson PX-8 User Manual

5.2 The IOBYTE
The PX-8 operating system supports 4 logical I/O devices, CON:, RDR:, PUN:
and LST: as described in Chapter 3.
In order to make it easy for the user, the
CP/M Utilities STAT enable devices to be assigned using these names.
In software terms the logical and physical devices are assigned using the ad-
dress 0003H in the main memory bank which contains a byte whose contents
decide the logical
to physical device assignments. This byte is known as the 10-
BYTE. The contents of the IOBYTE assigns the logical to physical devices as
shown in the following table.
Table 5.1
Logical device LST:
PUN: RDR: CON:
Bit position 7
or 6
5 or 4 3 or 2
lor 0
~
Bit pair Output Output Input Output Input
value (Binary)
00
Serial
Keyboard RS-232C
Keyboard
(printer)
-
01
LCD LCD
-
*LCD *Keyboard
10
*RS-232C *RS-232C *RS-232C LCD RS-232C
11
- -
-
RS-232C RS-232C
The default setting of the IOBYTE is 10101001. (Hexadecimal A9) This gives the
default assignments as shown
by the asterisks in the table.
Further information
on the assignments can be found in Chapter 3, sections 3.6
and
3.8.
5-2
5.3 The File Control Block (FCB)
During file operations, the operating system obtains file information from a
table called the file control block (FCB). The information included in the FCB
is as shown below.
Dr: Decimal
0:
1:
2:
3:
4:
5:
6:
7:
8:
Drive code
use logged-in drive
use Drive A:
use Drive
B:
use Drive C:
use Drive D:
use Drive E:
use Drive F:
use Drive G:
use Drive
H: the microcassette drive
F1 - F8: contain the file name in upper case ASCII
T1 - T3: contain the file type in upper case ASCII
Ex: Current extent number
Sl: Reserved for system
S2: Reserved for system
Rc: Record count
DO - DIS: Assigned by operating system.
Cr: Record counter
RO - R2: Random access record counter
Fig. 5.2
The CCP provides a FCB in the system work area which is called a TFCB (tem-
porary FCB); this is used as the default FCB.
5-3

Epson PX-8 Specifications

General

Brand	Epson
Model	PX-8
Category	Laptop
Language	English

Summary

Chapter 1 Overview

1.2 Hardware Configuration

Describes the PX-S hardware components, including CPU, memory, keyboard, display, and interfaces.

1.3 Software Configuration

Chapter 2 Starting Up and Operating the PX-8

2.1 Starting Up

Provides precautions for computer and AC adapter usage, and procedures before switching on the PX-8.

2.2 Operating The Computer

Details operating the computer, including keyboard functions, special keys, and screen modes.

2.2.2 Switching the PX-8 on and off

2.2.4 Alternative reset sequences

Chapter 3 Operating the Computer Under CP/M

3.1 What Is CP/M?

Introduces CP/M as a popular operating system for microcomputers and its advantages.

3.2 Files And File Names

Explains file storage, naming conventions, primary names, extensions, and wildcards.

3.3 Starting To Use CP/M

Details using CP/M, including disk drive names, changing disks, and warm starts.

3.4 Using The Keyboard Under CP/M

Describes keyboard functions under CP/M, including programmable function keys and character deletion.

3.6 The Concept of Logical And Physical Devices

3.7 The CP/M Built-In Commands

Lists and explains essential CP/M built-in commands like DIR, ERA, REN, SAVE, TYPE, and USER.

3.8 Using Utilities and Application Program with CP/M

Covers CP/M utilities (PIP, STAT, SUBMIT, XSUB, CONFIG, TERM) and application programs.

3.8.6 CONFIG

Chapter 4 Input and Output Devices and Optional Additions to the PX-8

4.1 Storage of Files and Data

Discusses file storage options including Microcassette drive and optional floppy disk drives.

4.1.1 Microcassette Drive

4.2 RS-232C Interface

Explains the RS-232C interface, its operation modes, protocols, and examples of use.

4.3 Serial Interface

4.4 Using Printers with the PX-8

Chapter 5 The System Interface

5.1 The CP/M Configuration

5.2 The IOBYTE

5.3 The File Control Block (FCB)

5.4 BDOS Function Calls

5.6 The BIOS Interface

5.7 The Entry Address of the BIOS Subroutines